The present invention relates to a method of preparing an aqueous dispersion of poly(perfluorovinyl ether)homopolymers. The present invention further relates to a method of making an aqueous fluoropolymer dispersion comprising bicomponent particles of poly(perfluorovinyl ether)homopolymers and a second fluoropolymer. The dispersions of the present invention may be used for rendering fibrous substrates oil repellent, water repellent and/or stain repellent. The invention further relates to fibrous substrates, in particular textiles, treated with the fluorochemical composition and to a method of treating the fibrous substrate with the fluorochemical dispersions.
Compositions for making substrates, in particular fibrous substrates, such as textiles, oil- and water repellent have been long known in the art. When treating fibrous substrates and in particular textile such as apparel, it is a requirement that the textile retains its look and feel as much as possible. Therefore, the amount of composition that can be applied in any treatment to provide repellency properties to the substrates is limited because large amounts would result in disturbing the look and feel of the substrate and would make them useless for many applications. As a result, the composition used for treating the substrates need to be effective at low application levels.
Fluorochemical compounds have been well known as being highly effective in providing oil and water repellency to substrates and in particular textile substrates. The commercially available fluorochemical compositions can be applied at low levels and are generally effective in providing the desired oil and water repellency properties at these low levels.
Fluorochemicals taught for treating textile include polymers based on vinyl ethers that have a perfluoroalkyl group. For example, U.S. Pat. No. 4,929,471 discloses the use of a copolymer of CH2xe2x95x90CHxe2x80x94OR wherein R may represent a fluorinated group for treating polyester fabric during its manufacturing process so as to produce a polyester fabric that has similar physical properties as silk or rayon.
U.S. Pat. No. 4,029,867 discloses to provide soil repellency and soil release properties to textile using a copolymer of maleic anhydride and a comonomer of the formula CH2xe2x95x90CHxe2x80x94CH2xe2x80x94Oxe2x80x94Rf wherein Rf represents a perfluorinated group. A homopolymer of CH2xe2x95x90CHxe2x80x94Oxe2x80x94Rf is disclosed in DE 1720799 and is mentioned to be suitable for rendering textile oil and water repellent. The aforementioned fluorochemical compositions are all based on fluorine containing polymers that do not have a fluorinated backbone.
Fluoropolymers having a fluorinated backbone such as for example polytetrafluoroethylene (PTFE) and copolymers of tetrafluoroethylene (TFE), have been known for coating substrates to provide various properties to the substrate including repellency properties. Fluoropolymers have for example been coated on cookware to provide desired release properties thereto. Fluoropolymers having a fluorinated backbone are disclosed in U.S. Pat. Nos. 4,546,157, 4,619,983, 4,766,190, 5,110,385, 5,969,066, 3,450,684, 4,035,565, 4,368,308, 4,418,186, 4,654,394, 4,840,998, 5,639,838 and 3,136,745. However, to be effective as a repellent coating, it has been taught to apply fluoropolymer coatings in high amounts. Such thick coatings are however unsuitable for treating textiles as they change the look and feel of the textile substrate substantially, i.e. to the extent such textiles are unsuitable for use in apparel. Sometimes, such coatings are subsequently subjected to a sintering step at high temperatures that would generally destroy many of the fibrous substrates desired for treatment.
EP 969 055 for example discloses an aqueous dispersion containing PTFE and a copolymer of TFE and a perfluorovinyl ether (PVE) for coating substrates such as ceramics or to impregnate textile. However, the amount of fluoropolymer in the treatment solution is at least 25% by weight resulting in a fairly thick coating. Moreover, the coating is subjected to a sintering step at a temperature of 420xc2x0 C. which would destroy many fibrous materials used for apparel.
U.S. Pat. No. 4,670,328 discloses aqueous dispersions of certain copolymers of TFE and PVE for the impregnation of textiles. Again, the level of fluoropolymer applied in the impregnation is so large that the look and feel of the textile is substantially affected. Accordingly, the impregnated materials are generally only useful in specialized applications such as dust free clothes or chemical resistant clothes where the appearance of the clothes is of secondary consideration.
EP 186186 discloses a curable fluoroolefin polymer for making coatings that have high weatherability and good repellency properties such as water repellency, oil repellency and/or stain repellency. However, a thick coating is apparently required to achieve these properties.
Fluorochemical compositions for rendering fibrous substrates oil- and/or water repellent are described in Applicant""s co-pending application U.S. Ser. No. 09/861,782 filed May 21, 2001. The compositions comprise up to 4% by weight of a fluoropolymer having a fully- or partially fluorinated backbone and comprise repeating units of the formula xe2x80x94CF2xe2x80x94CFRfxe2x80x94, where Rf is a perfluorinated organic group having a chain length of at least two atoms and having at least one carbon atom.
Although perfluorovinyl ether homopolymers have been prepared, and copolymers of perfluorovinyl ethers have been used in textile treatments, the difficulty in preparing perfluorovinyl ether homopolymers have heretofore prohibited their use in textile treatments. It would thus be desirable to find alternative fluorochemical compositions that do not display many of the disadvantages of the fluorochemical compositions in the prior art. In particular, it would be desirable to find fluorochemical compositions comprising perfluorovinyl ether homopolymers that are effective in providing oil and water repellency to a fibrous substrate, in particular a textile substrate, without substantially adversely affecting the appearance of the textile, i.e. such that the fibrous substrate is suitable for use in apparel. Preferably, the fluorochemical compositions are also capable of providing soil repellency and soil release properties to the fibrous substrate. Desirably, the fluorochemical compositions will be more environmental friendly and sufficiently stable to substantially avoid formation of low molecular weight fluorinated substances. The fluorochemical compositions are preferably also compatible with commonly used textile treatments and are preferably easy to apply by a customer in a reproducible and reliable way. Finally, the desired fluorochemical compositions are preferably capable of providing durable repellency properties to a fibrous substrate.
The present invention provides a method of making a poly(perfluorovinyl ether) homopolymer dispersion comprising the steps of:
a) pre-emulsifying an aqueous mixture of a perfluorovinyl ether in the presence of a fluorochemical emulsifier to an average emulsion droplet size of 1 micron or less, and
b) polymerizing said perfluorovinyl ether in the presence of a free-radical initiator at temperature and for a time sufficient to produce particles of poly(perfluorovinyl ether).
The perfluorovinyl ether used in the present invention of claim 1 are of the formula: CF2xe2x95x90CFxe2x80x94Rf, wherein Rf represents a perfluorinated organic group having a chain length of at least 2 atoms and having at least one carbon atom and at least one oxygen atom. The Rf group may be a perfluoroalkoxy group, a perfluoroether group or a perfluoropolyether group.
The present invention further provides a method of making a fluoropolymer dispersion comprising bicomponent particles comprising the steps of:
a. pre-emulsifying an aqueous mixture of a perfluorovinyl ether monomer in the presence of a fluorochemical emulsifier to an average emulsion droplet size of one micron or less, and
b. polymerizing said perfluorovinyl ether in the presence of a free-radical initiator at temperature and for a time sufficient to produce particles of poly(perfluorovinyl ether),
c) subsequently adding at least one additional fluorinated co-monomer without additional fluorochemical emulsifier, and
d) further polymerizing the resulting mixture.
As used herein a xe2x80x9cbicomponent particlexe2x80x9d is a single particle of two distinct fluoropolymers. The first fluoropolymer is a homopolymer of one or more perfluorovinyl ether monomers. The second fluoropolymer may be any fluoropolymer comprising one or more fluoromonomers, such as tetrafluoroethylene homo- or copolymers, vinylidene fluoride homo- or copolymers, or hexafluoropropylene homo- or copolymers or perfluorovinyl ether homo- or copolymers. The bicomponent particle may comprise a core-shell, inverted core-shell, half-moon, or other morphologies.
In a further aspect, the present invention provides a fluoropolymer dispersion for rendering a fibrous substrate oil and/or water repellent. The fluorochemical dispersion may comprise particles of poly(perfluorovinyl ether) homopolymer or may comprise bicomponent particles of poly(perfluorovinyl ether) homopolymer and a second component fluoropolymer.
In a still further aspect, the invention relates to a fluoropolymer dispersion that comprises a bicomponent particle comprising a first poly(perfluorovinyl ether) and a second fluoropolymer. The first fluoropolymer consists essentially of repeating units corresponding to the general formula: 
wherein Rf represents a perfluorinated organic group having a chain length of at least 1 oxygen atom and having at least one carbon atom.
Such dispersions of bicomponent particles have been found to be particularly effective for the treatment of fibrous substrates. In particular it was found that the second fluoropolymer contributed to an improvement of the repellency properties often going beyond a mere addition of the oil repellency properties of the fluoropolymers on their own, particularly with an auxiliary component as described below. Accordingly, the cost of a fluorochemical treatment composition may thereby be lowered as the cost of the first poly(perfluorovinyl ether)homopolymer is generally higher than that of the second fluoropolymer.
The fluoropolymer dispersion of the present invention has been found to be effective for providing oil repellency and/or water repellency properties to a fibrous substrate without substantially affecting the appearance thereof. Furthermore, the fluoropolymer dispersion may be produced such that the amount of low molecular weight species (less than 1000 g/mol) in the composition is low, e.g. not more than 0.5% by weight, preferably not more than 1000 ppm, or is even free of such substances. Also, the fluoropolymer dispersions generally will have a high chemical stability such that the fluoropolymer dispersions generally do not form low molecular weight fluorinated substances over a long period of time. The fluoropolymer dispersion may further provide soil repellency as well as soil or stain release properties. With the term soil and stain release is meant that a treated substrate that becomes soiled or stained can be more easily cleaned in for example a home laundering than an untreated substrate that becomes soiled or stained. Soil/stain repellency on the other hand refers to the ability to repel soil thereby reducing soiling or staining of the substrate.
The amount of the fluoropolymer in a treatment composition will typically be selected in order to achieve the desired level of fluoropolymer on the substrate to be treated. Typically the amount of the fluoropolymer in the treatment composition is not more than 4% by weight (based on the total weight of the composition), for example between 0.01% by weight and 4% by weight, preferably between 0.05% and 3% by weight. Higher amounts of the fluoropolymer can be used as well, particularly in cases where the uptake of the composition by the fibrous substrate is low.
In a further aspect, the present invention relates to a treatment of fibrous substrates with the above fluorochemical compositions. The substrates so obtained generally have good repellency properties such as oil repellency, water repellency, soil repellency. Additionally, the treated substrates may exhibit good or improved soil/stain release properties as well.
In a still further aspect of the present invention there are provided fibrous substrates, in particular textiles, that have coated on at least part of at least one major surface, the fluoropolymer dispersion of the invention. The amount of the fluoropolymer on such a treated fibrous substrate should generally be less than 3% by weight based on the weight of the fibrous substrate so as to preserve the general look and feel of the substrate although the amount that can be applied without adversely affecting the look and feel of the substrate will depend on the nature of both the substrate as well as the fluorochemical composition used in the treatment.
In yet another aspect, the invention relates to the use of a fluoropolymer dispersion to impart oil repellency, water repellency, soil repellency and/or soil/stain release to a fibrous substrate without substantially affecting the look and feel of said fibrous substrate, the fluorochemical composition comprising a solution or dispersion of a fluoropolymer having fully fluorinated backbone and comprising one or more repeating units corresponding to the general formula: 
wherein Rf represents a perfluorinated organic group having a chain length of at least 1 oxygen atom and having at least one carbon atom. By the term xe2x80x9cwithout substantially affecting the look and feel of said fibrous substratexe2x80x9d is meant that the treated substrate does not differ substantially in appearance from the untreated substrate such that the treated substrate can be used without objection in applications such as for example apparel, where the look and feel of the fibrous substrate are a major consideration for its use.
Finally, the invention relates to fluorochemical compositions that comprise a dispersion of the aforementioned fluoropolymer(s) and further an auxiliary component, generally a non-fluorinated organic compound, that is capable of further improving the water and/or oil repellency and/or the soil/stain release properties of a fibrous substrate treated with the fluorochemical composition.